1. Field of the Invention
The present invention is generally related to a method for separating nanoparticles, and more particularly to a method for separating nanoparticles with a controlled number of active groups.
2. Description of the Prior Art
Nanoparticle labels with a discrete and controlled number of attached ligands (or even more general: functional groups) would be very desirable. Dependent on material, size, and shape, nanoparticles can have different functionalities, such as fluorescence, phosphorescence, optical absorption, or magnetic moment, and can thus be detected with different techniques. Ligand molecules attached to the surface of such nanoparticles will specifically bind to their corresponding receptors. Such constructs, as for instance gold or semiconductor nanoparticles decorated with oligonucleotides, streptavidin or antibodies, have been successfully used in life sciences to trace the position of single proteins within the membrane of living cells, and to visualize the structure of artificially created nanostructures.
One key issue for some of the above-mentioned applications is the ability to control the number of ligand molecules bound to each nanoparticle. By exactly controlling the number of binding sites per nanoparticle unwanted crosslinking effects between the labels or between the structures to be labeled, which eventually can lead to agglomeration, can be avoided. For the controlled assembly of nanoparticle groupings such defined building blocks are a prerequisite. Except few cases, so far it has not been possible to directly synthesize such nanoparticles. Therefore, new method for separating nanoparticles with a controlled number of active groups is still needed corresponding to both economic effect and utilization in industry.